Arc detection is an enhancement to thermal and magnetic overload detection typically used in circuit breakers, which may not otherwise detect and respond to arc faults. A number of devices for detecting arc faults and methods of detection have been used in the past. These include E and B field arc sensors, detecting the magnitude of the rate of change of current signals when an arc fault occurs, the use of non-overlapping band pass filters to detect white noise characteristic of arcs, and detecting the disappearance of signals indicating the presence of arcs near zero current crossings. While some of these techniques are more or less effective, they require relatively sophisticated arc sensors and circuits. Heretofore, most arc detection circuits have been incorporated in circuit breakers because, among other things, the circuits were too large to fit in a wiring device such as a receptacle.
There is a need for simple economical arc fault detectors that can be included in wiring devices such as receptacles, plugs, or in-line devices, and that offer the same protection as an arc fault detector incorporated in a circuit breaker, but at lower cost. There is a need for an arc fault detector in wiring devices that can be provided at a reduced cost compared with arc fault detecting circuit breakers which is comparable to the reduction in cost achieved between ground fault interrupting receptacles and ground fault interrupting circuit breakers. There is a need for a sensor and associated circuitry for an AFCI that is miniaturized. There is also a need for a sensor and associated circuitry that effectively senses and allows protection against both arc faults and power line grounded neutral faults.